Reconstructing the Caledonian orogeny in West Pontides: Tectono-magmatic signatures from the İstanbul–Zonguldak Tectonic Unit

IF 1.2 4区地球科学 Q2 Earth and Planetary Sciences

Proceedings of the Geologists Association Pub Date : 2026-02-01 Epub Date: 2025-10-22 DOI:10.1016/j.pgeola.2025.101153

Fatih Şen

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引用次数: 0

Abstract

New U–Pb zircon geochronology and geochemical data from slightly folded gabbro dykes intruding pre-Devonian strata in the İstanbul Terrane (İstanbul–Zonguldak Tectonic Unit, NW Turkey) constrain a Silurian magmatic episode (434.3 ± 4.0 Ma and 428.5 ± 2.2 Ma) associated with syn-collisional alkaline magmatism. Despite within-plate trace element signatures (notably positive Nb anomalies), tectonic discrimination diagrams indicate emplacement within a syn-collisional regime, consistent with slab break-off following soft docking between Far East Avalonia and Baltica. High-intensity zircon overgrowths yield concordant Early Devonian ages (c.416–415 Ma), interpreted as a distal Caledonian tectono-thermal overprint. The Th/U ratios and cathodoluminescence textures of these domains support deformation-related recrystallisation rather than magmatic or metamorphic zircon growth. Structurally, folded geometries and axial-plane cleavage in the dykes are consistent with this event. These data imply that the İstanbul Terrane records a previously unrecognised disconformity at the Silurian–Devonian boundary, correlating with the established unconformity in the Zonguldak Terrane. This stratigraphical gap, masked by urbanisation in the İstanbul region, aligns with regional deformations of the Caledonian orogeny across Avalonian fragments.

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重建西庞德斯加里东造山运动：来自İstanbul-Zonguldak构造单元的构造-岩浆特征

来自土耳其西北部İstanbul地块（İstanbul-Zonguldak构造单元）侵入前泥盆世地层的微褶皱辉长岩岩脉的新U-Pb锆石年代学和地球化学数据，约束了与同碰撞碱性岩浆作用有关的志留纪岩浆事件（434.3 ± 4.0 Ma和428.5 ± 2.2 Ma）。尽管板块内有微量元素特征（特别是正Nb异常），但构造判别图表明侵位处于同碰撞状态，与远东阿瓦洛尼亚和波罗的海之间软对接后的板块断裂相一致。高强度的锆石过度生长产生了一致的早泥盆世时代（c.416-415 Ma），被解释为远加里东构造-热叠印。这些区域的Th/U比值和阴极发光结构支持与变形有关的再结晶，而不是岩浆或变质锆石生长。构造上，褶皱几何形状和岩脉的轴面解理与此事件一致。这些资料表明İstanbul地体记录了志留系—泥盆系界线上以前未被认识到的不整合，与宗古达克地体已建立的不整合相对应。这种地层差距被İstanbul地区的城市化所掩盖，与加里东造山运动在阿瓦洛尼亚碎片上的区域变形一致。

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来源期刊

Proceedings of the Geologists Association 地学-地质学

CiteScore

2.70

自引率

8.30%

发文量

审稿时长

6-12 weeks

期刊介绍： The Proceedings of the Geologists'' Association is an international geoscience journal that was founded in 1859 and publishes research and review papers on all aspects of Earth Science. In particular, papers will focus on the geology of northwestern Europe and the Mediterranean, including both the onshore and offshore record. Following a long tradition, the PGA will focus on: i) a range of article types (see below) on topics of wide relevance to Earth Sciences ii) papers on aspects of Earth Science that have societal relevance including geoconservation and Earth management, iii) papers on palaeoenvironments and palaeontology of the Mesozoic and Cenozoic, iv) papers on aspects of Quaternary geology and climate change, and v) papers on the history of geology with particular reference to individuals that have shaped the subject. These topics will also steer the content of the themes of the Special Issues that are published in the PGA.